In recent years, technologies for an IC chip (also referred to as an IC tag, an ID tag, an RF (Radio Frequency) tag, a wireless tag, or an electronic tag) using a thin film integrated circuit formed over a glass substrate have been developed. In such technologies, a thin film integrated circuit formed over a glass substrate needs to be separated from the glass substrate, which is a supporting substrate, after the completion. Accordingly, various techniques have been invented so far to separate a thin film integrated circuit provided over a supporting substrate.
For example, a substrate may be thinned by grinding or polishing to obtain a thin film integrated circuit out, a supporting substrate may be removed by chemical reaction or the like, or a thin film integrated circuit may be peeled off a supporting substrate.
As a specific method for peeling off a thin film integrated circuit provided over a supporting substrate, there is a technique for providing a space and separating a supporting substrate, by providing a separation layer of amorphous silicon (or polysilicon) and irradiating the same with laser light through the substrate to release hydrogen contained in amorphous silicon (Reference 1: Japanese Patent Laid-Open No. 10-125929). Further, there is a technique for separating a thin film integrated circuit from a supporting substrate, by providing a release layer containing silicon between the thin film integrated circuit and the supporting substrate and removing the same using a gas containing halogen fluoride (Reference 2: Japanese Patent Laid-Open No. 8-254686). Thus, there are many ways to separate a thin film integrated circuit provided over a supporting substrate.
However, in the case of removing a supporting substrate by grinding, polishing, or dissolution, it is very difficult to reuse a substrate that has been used once and cost is high.
In the case of separating a thin film integrated circuit provided over a supporting substrate by removing a release layer provided between the thin film integrated circuit and the supporting substrate, removal of the release layer becomes important. In other words, time needed to remove the release layer, the state of the thin film integrated circuit after the removal, and the like are dependent on the selection of a material used for the release layer and an etchant. Consequently, the step of peeling the thin film integrated circuit from the supporting substrate greatly affects the production efficiency, total cost, and the like. In addition, in the peeling step using the release layer, the thin film integrated circuit is distorted due to stress or the like when the thin film integrated circuit provided over the supporting substrate is separated, so that it is difficult to maintain its original shape.